.scroll-to-top-btn {
  display:flex;border-radius:50%;box-shadow:.1rem .1rem 1rem rgba(0,0,0,.3)
}
.scroll-to-top-btn {
  width:4rem;height:4rem;justify-content:center;align-items:center;padding:.5rem;overflow:hidden;border:none
}
.scroll-to-top-btn svg {
  width:2.2rem;height:2.2rem;pointer-events:none
}
.scroll-to-top-btn {
  --sticky-atc-offset:0px;position:fixed;transition:.15s ease-in-out;bottom:calc(var(--offset-y) + var(--sticky-atc-offset));z-index:2
}
.scroll-to-top-btn-bottom-left {
  left:var(--offset-x)
}
.scroll-to-top-btn-bottom-center {
  left:50%;transform:translateX(-50%)
}
.scroll-to-top-btn-bottom-right {
  right:var(--offset-x)
}